I've a support case where I was requested to upgrade a X301 with some RAM, price was a big issue, so I found some Corsair CMSO8GX3M2A1600C11, 2x4gb modules, and ordered them. The client then proceeds to install them himself and gets the beepcode 1 long followed by 3 short, which indicates something wrong with DIMM or systemboard.

Now, I haven't been able to find any information that there should be a problem with installing 1600mhz 4gb modules in the X301. Is there a problem here? I haven't had a chance to get my own hands on the machine yet, so I sadly can't say if there's any fumbling with the installation. But I'd just like to hear if anyone has got any experience with upgrading RAM beyond base specs in this and how it handles clocking them down...

Happened to see this at the Lenovo forum a few hours after seeing your post:

Re: x300 memory Options
‎05-15-201312:30 PM - edited ‎05-15-201312:30 PM
I can confirm, my Lenovo X301 with 2x 4GB DDR3 Samsung 2Rx8 PC3 12800 working.
But unfortunatelly, in Lenovo X301 DDR-II adjusted chipset is used to get DDR3 memory working, so all the memory is running at 400MHz (800MHz respectively), so even though you are using 1600MHz memory (PC 12800) like me, they are running only at 800MHz.

91011 wrote:Happened to see this at the Lenovo forum a few hours after seeing your post:

Re: x300 memory Options
‎05-15-201312:30 PM - edited ‎05-15-201312:30 PM
I can confirm, my Lenovo X301 with 2x 4GB DDR3 Samsung 2Rx8 PC3 12800 working.
But unfortunatelly, in Lenovo X301 DDR-II adjusted chipset is used to get DDR3 memory working, so all the memory is running at 400MHz (800MHz respectively), so even though you are using 1600MHz memory (PC 12800) like me, they are running only at 800MHz.

Those are useful for all laptops, not just ThinkPads. Honestly, the only thing I find myself really wanting on a X301 is an externally-accessible SD card reader. That's been the sole drawback I don't understand.